Hydrogen production apparatus, hydrogen production method, silicon fine particles for hydrogen production, and production method for silicon fine particles for hydrogen production

ABSTRACT

An exemplary hydrogen production apparatus  100  according to the present invention includes a grinding unit  10  configured to grind a silicon chip or a silicon grinding scrap  1  to form silicon fine particles  2,  and a hydrogen generator  70  configured to generate hydrogen by causing the silicon fine particles  2  to contact with as well as disperse in, or to contact with or dispersed in water or an aqueous solution. The hydrogen production apparatus  100  can achieve reliable production of a practically adequate amount of hydrogen from a start material of silicon chips or silicon grinding scraps that are ordinarily regarded as waste. The hydrogen production apparatus thus effectively utilizes the silicon chips or the silicon grinding scraps so as to contribute to environmental protection as well as to significant reduction in cost for production of hydrogen that is utilized as an energy source in the next generation.

TECHNICAL FIELD

The present invention relates to a hydrogen production apparatus, ahydrogen production method, silicon fine particles for hydrogenproduction, and a production method for silicon fine particles forhydrogen production.

BACKGROUND ART

Fuel cells have recently been attracting attention as one of possibleenergy sources in the next generation in terms of resource exhaustionprevention and environmental protection. Accordingly, development intechnique of producing hydrogen included in fuel cells as fuelsubstituting for petroleum will largely influence success in upcomingdevelopment in the fuel cell field. There has been disclosed aconventional technique of producing hydrogen as such an energy source bycausing silicon fine powder having an average particle diameter of 2 μm(micron) or less to contact with water (e.g., Patent Document 1).

As to silicon powder, the inventors of the present application havedisclosed a method for producing silicon fine particles, other thangrinding a silicon wafer into fine particles, from silicon particlesso-called chip powder that is obtained upon forming a thin substrate(wafer) from a silicon base material (ingot). The inventors of thepresent application have also disclosed a technique of applying theobtained silicon fine particles to silicon ink or a solar cell (e.g.,Patent Document 2).

PRIOR ART DOCUMENT Patent Documents

Patent Document 1: JP 2004-115349 A

Patent Document 2: JP 2012-229146 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, the conventionally disclosed technique of producing hydrogenachieves a hydrogen gas generation amount only in the range from 0.2mmol (millimolar) to 2.9 mmol in a case where 15 g of silicon powder iscaused to react for one hour, and fails to reach an adequate generationamount for actual industrial application.

It is desired, in terms of effective resource utilization andenvironmental protection, to effectively utilize silicon particles thatare obtained from chips formed by cutting silicon or silicon grindingscraps, which are ordinarily dealt as waste.

The present invention solves at least one of the technical problemsmentioned above, and significantly contributes to achievement of ahydrogen production apparatus and a hydrogen production method thateffectively utilize silicon waste and are excellent in economical andindustrial efficiency.

Solutions to the Problems

The inventors of the present application have devoted themselves tointensive researches in a practically and industrially excellenthydrogen production technique by focusing on effective utilization ofsilicon fine scraps or chips (hereinafter, also generally called“silicon chips”) or silicon grinding scraps, which are ordinarilydiscarded as a large amount of waste, in silicon cutting in a productionprocess of semiconductor products in the semiconductor field. Theinventors finally have found that silicon waste can be utilizedeffectively and a large amount of hydrogen can be produced even under amoderate condition. The present invention has been devised in view ofthe above point.

An exemplary hydrogen production apparatus according to the presentinvention includes: a grinding unit configured to grind a silicon chipor a silicon grinding scrap to form silicon fine particles; and ahydrogen generator configured to generate hydrogen by causing thesilicon fine particles to contact with as well as disperse in, or tocontact with or dispersed in water or an aqueous solution.

This hydrogen production apparatus can achieve reliable production of apractically adequate amount of hydrogen from a start material of siliconchips or silicon grinding scraps that are obtained by silicon cutting ina production process of semiconductor products or the like and areordinarily dealt as waste. This hydrogen production apparatus thuseffectively utilizes silicon chips or silicon grinding scraps ordinarilyregarded as waste so as not only to significantly contribute toenvironmental protection, but also to achieve significant reduction incost for production of hydrogen that is utilized in a fuel cell or thelike as an energy source in the next generation. This hydrogenproduction apparatus can thus markedly improve industrial productivityin hydrogen production.

An exemplary hydrogen production method according to the presentinvention includes: a grinding step of grinding a silicon chip or asilicon grinding scrap to form silicon fine particles; and a hydrogengenerating step of generating hydrogen by causing the silicon fineparticles to contact with as well as disperse in, or to contact with ordispersed in water or an aqueous solution.

This hydrogen production method can achieve reliable production of apractically adequate amount of hydrogen from a start material of siliconchips or silicon grinding scraps that are obtained by silicon cutting ina production process of semiconductor products or the like and areordinarily dealt as waste. This hydrogen production method thuseffectively utilizes silicon chips or silicon grinding scraps ordinarilyregarded as waste so as not only to significantly contribute toenvironmental protection, but also to achieve significant reduction incost for production of hydrogen that is utilized in a fuel cell or thelike as an energy source in the next generation. This hydrogenproduction method can thus markedly improve industrial productivity inhydrogen production.

An exemplary silicon fine particle for hydrogen production according tothe present invention has an amorphous shape and a crystallite diameterdistribution in the range of 100 nm (nanometer) or less. Among siliconfine particles formed by grinding silicon chips or silicon grindingscraps, a silicon fine particle obtained through chemical treatment(typically, oxide film removal using an aqueous hydrofluoric acidsolution and/or an aqueous ammonium fluoride solution orhydrophilization using a fourth liquid in each embodiment to bedescribed later) preferably exemplify the above silicon fine particlesfor hydrogen production.

An exemplary production method for silicon fine particles for hydrogenproduction according to the present invention includes a grinding stepof grinding a silicon chip or a silicon grinding scrap to form siliconfine particles.

The silicon fine particles for hydrogen production and the productionmethod for the silicon fine particles for hydrogen production canachieve provision of an intermediate material that enables reliableproduction of a practically adequate amount of hydrogen from siliconchips or silicon grinding scraps that are obtained by silicon cutting ina production process of semiconductor products or the like and areordinarily dealt as waste.

Effects of the Invention

The exemplary hydrogen production apparatus according to the presentinvention and the exemplary hydrogen production method according to thepresent invention can achieve reliable production of a practicallyadequate amount of hydrogen from a start material of silicon chips orsilicon grinding scraps that are ordinarily regarded as waste. Thehydrogen production apparatus and the hydrogen production method thuseffectively utilize silicon chips or silicon grinding scraps regarded aswaste so as to contribute to environmental protection as well as tosignificant reduction in cost for production of hydrogen that isutilized as an energy source in the next generation. The exemplarysilicon fine particles for hydrogen production according to the presentinvention and the exemplary production method for the silicon fineparticles for hydrogen production can provide an intermediate materialthat enables reliable production of a practically adequate amount ofhydrogen from silicon chips or silicon grinding scraps that are obtainedby silicon cutting in a production process of semiconductor products orthe like and are ordinarily regarded as waste.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of respective steps in a hydrogen productionmethod according to a first embodiment.

FIG. 2 is a flowchart of respective steps in a hydrogen productionmethod according to a second embodiment.

FIG. 3 is a flowchart of respective steps in a hydrogen productionmethod according to a third embodiment.

FIG. 4 is an explanatory view depicting a schematic configuration of ahydrogen production apparatus according to a fourth embodiment.

FIGS. 5(a) and 5(b) are sectional TEM (transmission electron microscope)photographs each depicting a crystal structure of silicon fine particlesafter the grinding step in Example 1.

FIG. 6 is a crystallite diameter distribution graph of silicon fineparticles after the grinding step.

FIG. 7 is a graph of hydrogen generation amounts according to Examples 1to 3.

FIG. 8 is a graph of hydrogen generation amounts according to Examples 4and 5.

FIG. 9 is a graph of hydrogen generation amounts immediately after thestart of reaction in Examples 4 and 5.

FIG. 10 is an explanatory view depicting a schematic configuration of ahydrogen production apparatus according to a modification example of thefourth embodiment.

FIG. 11 is a graph of a hydrogen generation amount with respect to areaction period in Example 6.

FIG. 12 is a graph of a difference in maximum hydrogen generation speeddue to a difference in pH value in Example 6.

FIG. 13 is an XPS spectrography of silicon fine particles after hydrogengeneration reaction in Example 6.

FIG. 14 is a graph of a hydrogen generation amount per 1 g with respectto a reaction period in Example 7.

DESCRIPTION OF REFERENCE SIGNS

1 Silicon scrap material

2 Silicon fine particle

3 Silicon fine particle after surface oxide film removal

4 Silicon fine particle after hydrophilization treatment

5 Hydrogen

10 Grinder

14 Discharge port

15 Filter

30 Drying chamber

40 Rotary evaporator

50 Surface oxide film removal tank

57, 67, 77 Agitator

58 Centrifuge

60 Hydrophilization treatment tank

70 Hydrogen generator

72 Reaction tank

75 Water or aqueous solution

79 Transfer pipe

80 Water tank

87 Hydrogen collector

89 Hydrogen pipe

90 Hydrogen reservoir

100, 200 Hydrogen production apparatus

250 Additional surface oxide film removal tank

270 Additional hydrogen generator

EMBODIMENTS OF THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings. Common parts will bedenoted by common reference signs in all the drawings in this disclosureunless otherwise specified. Elements according to the respectiveembodiments will not always be depicted at relative scale ratios. Someof the reference signs may not appear in the drawings for better visual.

1. Hydrogen Production Method First Embodiment

A hydrogen production method according to the present embodimentincludes various steps of using an exemplary start material of siliconchips or silicon grinding scraps (hereinafter, also referred to as asilicon scrap material), which are obtained by silicon cutting in aproduction process of semiconductor products and are ordinarily regardedas waste. The silicon scrap material also includes fine scraps obtainedby grinding a waste wafer. FIG. 1 is a flowchart of the respective stepsin the hydrogen production method according to the present embodiment.As depicted in FIG. 1, the hydrogen production method according to thepresent embodiment includes the following steps (1) to (3).

(1) Washing step (51)

(2) Grinding step (S2)

(3) Hydrogen generating step (S3)

(1) Washing Step

The washing step (Si) according to the present embodiment includeswashing the silicon scrap material that is generated in a process ofcutting a monocrystal or polycrystal silicon ingot or the like. Thewashing step (Si) is executed mainly for removal of organic mattersadhering to the silicon scrap material, such as cutting oil and anadditive used in the process of cuttings. The silicon scrap material tobe washed is initially weighed, and then a predetermined first liquid isadded and the silicon scrap material is dispersed in the liquid by usinga ball mill. The ball mill according to the present embodiment is agrinder configured to grind a steel ball, a magnetic ball, a boulder,and a similar object. The first liquid according to the presentembodiment is, for example, acetone.

The silicon scrap material having been treated in the washing step iscaused to pass through a filter for removal of the first liquid by meansof suction filtration. The removed first liquid is disposed as a wasteliquid. The filtrated silicon scrap material is dried using a drier. Thedrying temperature according to the present embodiment is, for example,40° C. or higher and 60° C. or lower. The ball mill is used in thewashing step according to the present embodiment, so that it is possibleto markedly improve washing efficiency in comparison to simple immersionin the first liquid.

(2) Grinding Step

The subsequent grinding step (S2) includes grinding washed siliconsludge to form silicon fine particles having a crystallite diameter of100 nm or less. Such silicon fine particles having a crystallitediameter of 100 nm or less can achieve preferred effects, or effectssimilar to those of the present embodiment, even in a case where thesilicon fine particles have an aggregated particle distribution in therange of 100 nm or more and 5 μm or less. A predetermined second liquidis then added to the washed silicon sludge. The second liquid is, forexample, propanol. Rough grinding treatment is subsequently executedusing the ball mill. The roughly ground silicon scrap material is causedto pass through a filter for removal of relatively coarse particles, andthe remaining silicon scrap material is finely ground using a bead mill.The second liquid is subsequently removed using a rotary evaporator toobtain silicon fine particles as a finely ground object.

The grinding step (S2) according to the present embodiment enablesformation of silicon fine particles that have amorphous shapes, acrystallite diameter distribution in the range of 100 nm, andhydrophilic surfaces. The grinding step (S2) enables grinding treatmentby using any one selected from the grinder group consisting of a beadmill, a ball mill, a jet mill, and a shock wave grinder, or using anyone of combinations thereof.

(3) Hydrogen Generating Step

The subsequent hydrogen generating step (S3) includes generatinghydrogen by causing the silicon fine particles obtained in the grindingstep (S2) to contact with and/or disperse in water or an aqueoussolution. The water used in the hydrogen generating step is notnecessarily pure water but may be water containing an electrolyte or anorganic matter such as ordinary tap water or industrial water. Theaqueous solution according to the present embodiment is also notparticularly limited in terms of its type. The aqueous solution is notparticularly limited in terms of its hydrogen ion concentration index(pH value), but is more preferred to have a pH value of 10 or more. Itis because, the inventors have analyzed to find a tendency that a higherpH value leads to faster hydrogen generation speed and hydrogengeneration reaction is finished in a shorter period of time.Accordingly, in order to continuously supply a small amount of hydrogenfor a long period of time, the pH value of the aqueous solution isdecreased intentionally in a preferred aspect. In contrast, in order totemporarily supply a large amount of hydrogen, increase in pH value ofthe aqueous solution can achieve hydrogen production compliant withrequests from various industrial fields or users of various devices.

The water used in the hydrogen generating step can be set to anappropriate temperature for achievement of desired hydrogen generationspeed. Measures to cause the silicon fine particles to contact withand/or disperse in the water or the aqueous solution can be selectedfrom agitation, water current, shaking, and the like as necessary.Agitation or the like promotes hydrogen generation reaction, so thathydrogen production speed can be increased.

As described above, the hydrogen production method according to thepresent embodiment can achieve reliable production of a practicallyadequate amount of hydrogen from a start material of silicon chips orsilicon grinding scraps that are obtained by silicon cutting in aproduction process of semiconductor products or the like and areordinarily regarded as waste. Accordingly, the hydrogen productionmethod effectively utilize silicon chips or silicon grinding scrapsregarded as waste so as to contribute to environmental protection aswell as to significant reduction in cost for production of hydrogen thatis utilized as an energy source in the next generation. It is noted thatthe present embodiment can achieve production of a large amount ofhydrogen at the practical level without including a complicated step.

Second Embodiment

The present embodiment is similar to the first embodiment except that asurface oxide film removing step of removing oxide films on the surfacesof silicon fine particles is additionally executed after the grindingstep according to the first embodiment.

FIG. 2 is a flowchart of the respective steps in the hydrogen productionmethod according to the present embodiment. As depicted in FIG. 2, thehydrogen production method according to the present embodiment includesthe following steps (1) to (4).

(1) Washing step (T1)

(2) Grinding step (T2)

(3) Surface oxide film removing step (T3)

(4) Hydrogen generating step (T4)

As mentioned above, the washing step (S1), the grinding step (S2), andthe hydrogen generating step (S3) in the hydrogen production methodaccording to the first embodiment have the details overlapped with thosein the washing step (T1), the grinding step (T2), and the hydrogengenerating step (T4) according to the present embodiment. Accordingly,those steps other than the surface oxide film removing step (T3) willnot be described repeatedly.

The surface oxide film removing step (T3) will be described below.

The surface oxide film removing step (T3) includes causing the siliconfine particles obtained in the grinding step (T2) described above tocontact with an aqueous hydrofluoric acid solution or an aqueousammonium fluoride solution. According to the present embodiment, thesilicon fine particles that are obtained in the grinding step (T2) andhave a crystallite diameter in the range of 100 nm or less are immersedin the aqueous hydrofluoric acid solution or the aqueous ammoniumfluoride solution. The silicon fine particles are thus caused to contactwith and/or disperse in the aqueous hydrofluoric acid solution or theaqueous ammonium fluoride solution. The silicon fine particles and theaqueous hydrofluoric acid solution are subsequently separated using acentrifuge. The silicon fine particles are immersed in a third liquidsuch as an ethanol solution. The third liquid is then removed to obtainsilicon fine particles for hydrogen production.

The surface oxide film removing step according to the present embodimentincludes immersing the silicon fine particles in the aqueoushydrofluoric acid solution or the aqueous ammonium fluoride solution, sothat the silicon fine particles are caused to contact with the aqueoushydrofluoric acid solution or the aqueous ammonium fluoride solution.However, the surface oxide film removing step according to the presentembodiment is not limited into these modes. It is possible toalternatively adopt the step of causing the silicon fine particles tocontact with the aqueous hydrofluoric acid solution or the aqueousammonium fluoride solution in a different manner. According to adifferent adoptable aspect, the aqueous hydrofluoric acid solution orthe aqueous ammonium fluoride solution can be sprayed, in other words,showered, to the silicon fine particles.

The subsequent hydrogen generating step (T4) includes generatinghydrogen by causing the silicon fine particles after surface oxide filmremoval to contact with and/or disperse in water or an aqueous solution.

The hydrogen production method according to the present embodiment canachieve effects similar to those according to the first embodiment aswell as can achieve increase in hydrogen production amount by removingthe oxide films on the surfaces of the silicon fine particles.

Third Embodiment

The present embodiment is similar to the second embodiment except that ahydrophilization treatment step of hydrophilizing the surfaces of thesilicon fine particles is additionally executed after the surface oxidefilm removing step according to the second embodiment.

FIG. 3 is a flowchart of the respective steps in the hydrogen productionmethod according to the present embodiment. As depicted in FIG. 3, thehydrogen production method according to the present embodiment includesthe following steps (1) to (5).

(1) Washing step (U1)

(2) Grinding step (U2)

(3) Surface oxide film removing step (U3)

(4) Hydrophilization treatment step (U4)

(5) Hydrogen generating step (U5)

As mentioned above, the washing step (T1), the grinding step (T2), thesurface oxide film removing step (T3), and the hydrogen generating step(T4) in the hydrogen production method according to the secondembodiment have the details overlapped with those in the washing step(U1), the grinding step (U2), the surface oxide film removing step (U3),and the hydrogen generating step (U5) according to the presentembodiment. Accordingly, those steps other than the hydrophilizationtreatment step (U4) will not be described repeatedly.

The hydrophilization treatment step (U4) will be described below.

The hydrophilization treatment step (U4) according to the presentembodiment is executed after the surface oxide film removing step andincludes treating the surfaces of the silicon fine particles with asurfactant or nitric acid. Typical examples of the surfactant used forthe treatment include at least one selected from the group consisting ofan anionic surfactant, a cationic surfactant, and a nonionic surfactant.According to the present embodiment, the silicon fine particles arecaused to contact with and/or disperse in a fourth liquid such aspropanol, the surfactant or nitric acid is added, and the resultingliquid is agitated. The fourth liquid is removed using a rotaryevaporator after the agitation in the present embodiment.

The subsequent hydrogen generating step (U5) includes generatinghydrogen by causing the silicon fine particles after hydrophilizationtreatment to contact with and/or disperse in water or an aqueoussolution.

The hydrogen production method according to the present embodiment canachieve effects similar to those according to the first embodiment aswell as can decrease surface tension of the silicon fine particles bythe hydrophilization treatment step to reliably suppress the siliconfine particles from floating to the water surface, which is a phenomenonunique to fine particles. The silicon fine particles are thus wellblended with the water or the aqueous solution to achieve an increase incontact area between the silicon fine particles and the water or theaqueous solution and promotion of hydrogen generation reaction. It isthus possible to markedly increase the hydrogen production amount.

As described above, among the silicon fine particles formed by grindingsilicon chips or silicon grinding scraps, silicon fine particlesobtained through chemical treatment (typically, oxide film removaltreatment using the aqueous hydrofluoric acid solution or the aqueousammonium fluoride solution in the second embodiment, or hydrophilizationtreatment using the fourth liquid in the third embodiment) preferablyexemplify the silicon fine particles for hydrogen production accordingto each of the above embodiments. According to a preferred aspect interms of further promoted hydrogen generation, each of the aboveembodiments includes the chemical treatment step of chemically treatingthe silicon fine particles as described above.

2. Hydrogen Production Apparatus Fourth Embodiment

A hydrogen production apparatus 100 according to the present embodimentwill be described below. FIG. 4 is an explanatory view depicting aschematic configuration of the hydrogen production apparatus 100according to the present embodiment. As depicted in FIG. 4, the hydrogenproduction apparatus 100 according to the present embodiment mainlyincludes a grinder 10, a drying chamber 30, a rotary evaporator 40, asurface oxide film removal tank 50, a centrifuge 58, a hydrophilizationtreatment tank 60, a hydrogen generator 70, and a hydrogen reservoir 90.The hydrogen production apparatus 100 according to the presentembodiment is regarded as including collective devices (treatment units)configured to execute a plurality of steps to be described later. Thehydrogen production apparatus 100 may be called a hydrogen productionsystem.

The grinder 10 according to the present embodiment is a wet grinderconfigured to receive a treatment target along with a liquid and applygrinding, dispersing, and the like to the treatment target in theliquid. The grinder 10 is configured to be capable of executing thesteps of dispersing, mixing, grinding, etc., the treatment target andthe liquid thus fed. The grinder 10 can be configured by any oneselected from the grinder group consisting of a bead mill, a ball mill,a jet mill, and a shock wave grinder, or any one of combinationsthereof. In the hydrogen production apparatus 100 according to thepresent embodiment, the grinder 10 serves as a washing unit configuredto wash a silicon scrap material such as silicon chips or silicongrinding scraps generated in a silicon cutting process or the like, anda grinding unit configured to grind the washed silicon scrap materialinto silicon fine particles having a crystallite diameter of 100 nm orless.

The grinder 10 initially receives a silicon scrap material 1 as atreatment target and the second liquid according to the first embodimentthrough an input port 11 and washes the silicon scrap material 1. Thewashed silicon scrap material 1 as well as the second liquid are causedto pass through a filter 15 provided adjacent to a discharge port 14, sothat the second liquid is removed as waste liquid by means of suctionfiltration. The residue (silicon scrap material 1) is subsequently driedin the drying chamber 30, and is fed into the grinder 10 through theinput port 11 along with the second liquid so as to be ground.Specifically, the silicon scrap material 1 is roughly ground using aball mill or the like and the ground object as well as the second liquidare caused to pass through the filter 15 for removal of rough particles.The filtrated ground object is then finely ground using a bead mill orthe like. The finely ground object is subsequently collected and thesecond liquid is removed using the rotary evaporator 40 configured toautomatically perform vacuum distillation, to obtain silicon fineparticles 2.

The surface oxide film removal tank 50 exemplifying a surface oxide filmremover according to the present embodiment includes an agitator 57 andtreats the silicon fine particles 2 supplied from the grinder 10 with anaqueous hydrofluoric acid solution or an aqueous ammonium fluoridesolution 55. The centrifuge 58 subsequently separates silicon fineparticles 3 after surface oxide film removal from the aqueoushydrofluoric acid solution. In a case where the surface oxide films onthe surfaces of the silicon fine particles 2 are not removed, thesilicon fine particles 2 are fed to the hydrogen generator 70 to bedescribed later.

The hydrophilization treatment tank 60 exemplifying a hydrophilizationtreatment unit according to the present embodiment includes an agitator67 and causes the silicon fine particles 3 before or after surface oxidefilm removal to contact with and/or disperse in a fourth liquid 65 towhich a surfactant or nitric acid is added. In a case where the siliconfine particles 2 are not subjected to the hydrophilization treatment,the silicon fine particles before or after surface oxide film removalare fed to the hydrogen generator 70 to be described later. Silicon fineparticles before surface oxide film removal can be a target ofhydrophilization treatment according to the present embodiment. In orderfor more reliable hydrophilization of the silicon fine particles,hydrophilization treatment is preferably applied to silicon fineparticles after surface oxide film removal.

The hydrogen generator 70 according to the present embodiment includes areaction tank 72 provided with an agitator 77, a water tank 80, ahydrogen collector 87, a transfer pipe 79, and a hydrogen pipe 89. Inthe reaction tank 72, at least one selected from the group consisting ofthe silicon fine particles 2, the silicon fine particles 3 after surfaceoxide film removal, and silicon fine particles 4 after hydrophilizationtreatment are caused to contact with and/or disperse in water or anaqueous solution 75 to generate hydrogen 5. The generated hydrogen 5 isfed into water 85 in the water tank 80 via the transfer pipe 79. Thehydrogen 5 collected by the hydrogen collector 87 in accordance with anexemplary water substitute method is collected into the hydrogenreservoir 90 via the hydrogen pipe 89.

The hydrogen production apparatus 100 according to the presentembodiment can achieve relatively fast production of a practicallyadequate amount of hydrogen from a start material of silicon chips orsilicon grinding scraps that are obtained by silicon cutting in aproduction process of semiconductor products or the like and areordinarily regarded as waste.

EXAMPLES

Examples will be described below for more detailed description of theabove embodiments, but the above embodiments should not be limited tothese examples. Examples 1 to 5 to be described below refer to resultsof hydrogen production tests using the hydrogen production apparatus100.

Example 1

In Example 1, the hydrogen production apparatus 100 produced hydrogen inaccordance with the hydrogen production method of the first embodiment.Specifically, the hydrogen generating step was executed after thewashing step and the grinding step.

(1) Washing Step

Two hundred grams (g) of silicon chips was added to 200 milliliters (mL,also expressed as “ml”) of acetone, and dispersed for one hour by usinga ball mill. Used as the ball mill was a Universal BALL MILLmanufactured by MASUDA CORPORATION. The ball mill contained aluminabeads having particle diameters of 10 millimeters (mm) and 20 mm. Theliquid was then removed by means of suction filtration and the residuewas dried using a drier set to 40° C.

(2) Grinding Step

Subsequently, 15 g of washed silicon sludge is weighed and placed in aplastic container, to which 285 g of 2-propanol was added. Alumina ballsare then placed in a ball mill to perform rough grinding at acircumferential speed of 80 rpm for two hours. Used as the ball mill inthe present example is a Universal BALL MILL manufactured by MASUDACORPORATION. The balls used in the present example are alumina ballshaving particle diameters of 10 mm and 20 mm. The resultant obtained inthe grinding step was caused to pass through a mesh filter of 180 μm forremoval of coarse particles.

Alumina balls were then placed in a bead mill to perform fine grindingat a circumferential speed of 2908 rpm for four hours. The bead millused in the present example is a star mill LMZ015 manufactured byAshizawa Finetech Ltd. Used in the present example were 456 g ofzirconia beads having a particle diameter of 0.5 mm. The finely groundparticles were then collected and 2-propanol was removed using a rotaryevaporator to obtain silicon fine particles.

(3) Hydrogen Generating Step

Immersed in 50.21 g of ultrapure water were 0.86 g of silicon fineparticles for hydrogen production. The test was executed at normaltemperature (about 25° C.) in the present example.

Example 2

In Example 2, the hydrogen production apparatus 100 produced hydrogen inaccordance with the hydrogen production method of the second embodiment.Example 2 was performed in the same manner as in Example 1 except thatthe surface oxide film removing step was additionally executed after thegrinding step of Example 1. Specifically, hydrogen was produced throughthe washing step, the grinding step, the surface oxide film removingstep, and the hydrogen generating step in the mentioned order. Thesurface oxide film removing step is executed in the following manner.

In the surface oxide film removing step, the silicon fine particlesobtained in the grinding step of the present example are dispersed in a50% aqueous hydrofluoric acid solution. Subsequently, the silicon fineparticles are separated from the aqueous hydrofluoric acid solution byusing a centrifuge. The obtained silicon fine particles were thenimmersed in an ethanol solution. The ethanol solution was subsequentlyremoved to obtain silicon fine particles for hydrogen production.

Example 3

In Example 3, the hydrogen production apparatus 100 produced hydrogen inaccordance with the hydrogen production method of the third embodiment.Example 3 was performed in the same manner as in Example 2 except thatthe hydrophilization treatment step of treating using a surfactant wasadditionally executed after the surface oxide film removing step ofExample 2.

Specifically, the washing step, the grinding step, and the surface oxidefilm removing step were executed in the same manner as in Example 2. Inthe hydrophilization treatment step with use of the surfactant,2-propanol as the fourth liquid of the third embodiment was prepared toinclude silicon fine particles at a concentration of 5 wt %. Added tothis liquid was 0.05% polyoxyethylene nonyl phenyl ether (“Nonion NS206”produced by NOF CORPORATION) as a nonionic surfactant, and the obtainedliquid was agitated for one hour. Subsequently, 2-propanol was removedusing a rotary evaporator.

In the hydrogen generating step, 50.21 g of ultrapure water was added to0.86 g of silicon fine particles for hydrogen production to immerse thesilicon fine particles at normal temperature.

Example 4

Example 4 was performed in the same manner as in Example 2 by using thehydrogen production apparatus 100 except that a buffer solutioncontaining 0.1 mol/L of sodium bicarbonate and 0.1 mol/L of sodiumcarbonate was used to adjust the pH value of the aqueous solution forthe hydrogen generating step to 10 in the hydrogen production methodaccording to the second embodiment.

Example 5

Example 5 was performed in the same manner as in Example 2 by using thehydrogen production apparatus 100 except that 0.1 mol/L of an aqueouspotassium hydroxide solution was used to adjust the pH value of theaqueous solution for the hydrogen generating step to 13 in the hydrogenproduction method according to the second embodiment.

<Analysis Results of Examples> 1. Crystal Structure Analysis UsingSectional TEM Photographs

FIGS. 5(a) and 5(b) are sectional TEM (transmission electron microscope)photographs each depicting a crystal structure of silicon fine particlesafter the grinding step in Example 1. FIG. 5(a) depicts a state wherethe silicon fine particles are partially aggregated to form slightlylarger fine particles in amorphous shapes. On the other hand, FIG. 5(b)is a TEM photograph focusing on the individual silicon fine particles.As indicated in a central circle in FIG. 5(b), there was found a siliconfine particle having a diameter of about 5 nm or less. It was also foundthat this silicon fine particle has a crystalline property.

2. Crystallite Diameter Distribution of Silicon Fine Particles inAccordance with X-Ray Diffraction Method

FIG. 6 is a graph of analysis results according to the X-ray diffractionmethod, on crystallite diameter distribution of silicon fine particlesafter the grinding step. The graph in FIG. 6 as the transverse axisindicating the crystallite diameter (nm) and the ordinate axisindicating frequency. The solid line indicates number-based crystallitediameter distribution whereas the broken line indicates volume-basedcrystallite diameter distribution. According to the number distribution,the crystals had a mode diameter of 1.97 nm, a median diameter (50%crystallite diameter) of 3.70 nm, and an average diameter of 5.1 nm.According to the volume distribution, the crystals had a mode diameterof 13.1 nm, a median diameter of 24.6 nm, and an average diameter of33.7 nm. It was found from these results that the silicon fine particlesobtained after the grinding step according to the bead mill method areso-called silicon nanoparticles having crystallite diameters that are inthe range of 100 nm or less, and are distributed particularly in therange of 50 nm or less.

3. Hydrogen Production Amount

FIG. 7 is a graph of measurement results of hydrogen generation amountsaccording to Examples 1 to 3. The graph in FIG. 7 has the transverseaxis indicating the immersion period (minute) and the ordinate axisindicating the hydrogen generation amount (mL/g) per g of silicon fineparticles for hydrogen production.

As indicated in FIG. 7, in Example 1 not including the surface oxidefilm removing step, 10.7 ml of hydrogen was obtained for the immersionperiod of 7905 minutes.

As indicated in FIG. 7, in Example 2 in which the hydrogen productionapparatus 100 produced hydrogen in accordance with the hydrogenproduction method of the second embodiment, the reaction came into anequilibrium state after the immersion period of 5700 minutes (i.e., 95hours), and about 54.1 mL of hydrogen was obtained. In Example 1, alarge amount as much as 50 mL to 60 mL of hydrogen was finally producedper g of silicon fine particles for hydrogen production, as asignificantly preferred result.

In Example 3, 116.7 mL of hydrogen was obtained by immersion for 9805minutes (i.e., about 163 hours), as a more preferred result incomparison to Example 2. It is particularly found that the hydrogengeneration amounts of Examples 2 and 3 for 500 minutes or 1000 minutesfrom the start of reaction are much more than the hydrogen generationamount of Example 1. In other words, it is found that Examples 2 and 3achieve extremely fast hydrogen generation speed for 500 minutes or 1000minutes from the start of reaction. FIG. 7 thus indicates thesignificant effect of the surface oxide film removing step or thesurface oxide film remover.

Subsequently studied were results of Examples 4 and 5 including thehydrogen generating step of causing silicon fine particles to react withan aqueous solution having a high pH value. FIG. 8 is a graph ofmeasurement results of hydrogen generation amounts according to Examples4 and 5. FIG. 9 is a graph of hydrogen generation amounts for 60 minutesfrom the start of reaction in Examples 4 and 5. The graphs in FIGS. 8and 9 each have the transverse axis indicating the immersion period(minute) and the ordinate axis indicating the hydrogen generation amount(mL/g) per g of silicon fine particles for hydrogen production.

As indicated in FIG. 8, in Example 4 including the hydrogen generatingstep with use of the aqueous solution having a pH value of 10, thereaction came into a substantially equilibrium state after 5000 minutes(about 80 hours), and about 720 ml of hydrogen was obtained per g ofsilicon fine particles for hydrogen production. In contrast, in Example5 including the hydrogen generating step with use of the aqueoussolution having a pH value of 13, the reaction came into a substantiallyequilibrium state after 6254 minutes (about 104 hours), and about 942.1ml of hydrogen was obtained per g of silicon fine particles for hydrogenproduction. In such a case where the aqueous solution was brought intoan alkaline state so as to have a pH value of 10 or 13, there wasobtained a large amount of hydrogen as much as several to several tentimes in comparison to hydrogen obtained in Examples 1 to 3.

As indicated in the result of Example 5 in FIG. 9, with use of theaqueous solution having a pH value of 13 in the hydrogen generatingstep, the hydrogen generation amount rapidly increased immediately afterthe start of reaction between silicon fine particles and the aqueoussolution. More specifically, about 470 ml of hydrogen was generated perg of silicon fine particles for hydrogen production for 10 minutes, andabout 590 ml of hydrogen was generated per g of silicon fine particlesfor hydrogen production for 30 minutes. Furthermore, in Example 4including the hydrogen generating step with use of the aqueous solutionhaving a pH value of 10, about 3.5 ml of hydrogen was generated per g ofsilicon fine particles for hydrogen production for 13 minutes and about15 ml of hydrogen was generated per g of silicon fine particles forhydrogen production for 30 minutes. Example 4 could achieve generationof a larger amount of hydrogen in a shorter period of time in comparisonto Examples 1 to 3, although the reaction of Example 4 is more moderatethan that of Example 5.

It was thus found from FIGS. 8 and 9 that Examples 4 and 5 achievehydrogen generation speed much faster than that of Examples 1 to 3.Accordingly, it was found that increase in pH value (that is, adjustedto a pH value of 10 or more) of the aqueous solution used in thehydrogen generating step achieves reaction promoting fast hydrogengeneration in a short period of time, unlike moderate hydrogengeneration reaction for a long period of time as in Examples 1 to 3.According to a very preferred aspect, the pH value of the aqueoussolution used in the hydrogen generating step is set to 10 or more (14or less) in terms of faster generation of a larger amount of hydrogen.

The hydrogen production method and the hydrogen production apparatusdisclosed in each of the above embodiments are largely expected to beapplied to a technical field requiring hydrogen such as fuel cells. Thehydrogen production method and the hydrogen production apparatusaccording to each of the above embodiments have an interesting pointthat silicon chips or silicon grinding scraps are utilized as a startmaterial, which are obtained by silicon cutting in a production processof semiconductor products or the like and are ordinarily regarded aswaste. The cost for production of hydrogen per unit gram is thus muchcheaper than the cost for production of hydrogen according to aconventional hydrogen production method. Accordingly, this not onlycontributes to environmental protection through effective utilization ofwaste but also markedly improves economic efficiency of hydrogenproduction. Furthermore, the hydrogen production method and the hydrogenproduction apparatus according to each of the above embodiments do notrequire any complicated device, facility, or system, or any complicatedstep, and can thus significantly contribute to improvement in industrialproductivity.

Other Embodiments

In the reaction tank 72 of the hydrogen generator 70 according to thefourth embodiment, at least one selected from the group consisting ofthe silicon fine particles 2, the silicon fine particles 3 after surfaceoxide film removal, and the silicon fine particles 4 afterhydrophilization treatment are caused to contact with and/or disperse inthe water or the aqueous solution 75 to generate hydrogen. However, thereaction may come into an equilibrium state with elapse of time tosaturate the hydrogen generation amount or the hydrogen generationspeed. Disclosed as a solution to the problem are the configuration of ahydrogen production apparatus 200 according to a modification example ofthe fourth embodiment as depicted in FIG. 10 as well as Example 6.

FIG. 10 is an explanatory view depicting a schematic configuration ofthe hydrogen production apparatus 200 according to the modificationexample of the fourth embodiment. The hydrogen production apparatus 200according to the present embodiment is similar to the hydrogenproduction apparatus 100 according to the fourth embodiment except forincluding an additional hydrogen generator 270. As indicated by an arrow(R) in FIG. 10, the additional hydrogen generator 270 executes the stepof removing oxide films on the surfaces of silicon fine particles byextracting from the reaction tank 72 the silicon fine particles having ahydrogen generation amount or hydrogen generation speed once saturatedor almost saturated and then introducing the silicon fine particles intoan additional surface oxide film removal tank 250 configuring at leastpartially an additional surface oxide film remover in the hydrogenproduction apparatus 200 (the additional surface oxide film removingstep) and the subsequent step of generating hydrogen by feeding thesilicon fine particles, of which oxide films are removed, again into thereaction tank 72 (the additional hydrogen generating step). Accordingly,the overlapped description may not be disclosed repeatedly.

In the case where the hydrogen production apparatus 200 depicted in FIG.10 is used, even if the hydrogen generation amount or the hydrogengeneration speed is saturated or about to be saturated because thereaction in the reaction tank 72 once comes into an equilibrium state,the additional surface oxide film removing step subsequently executedrevitalizes hydrogen generation power of the silicon fine particles. Thehydrogen generation power of the silicon fine particles is revitalizedor recovered by executing the additional surface oxide film removingstep of causing the silicon fine particles to contact again with anaqueous hydrofluoric acid solution or an aqueous ammonium fluoridesolution during or after the hydrogen generating step in each of theabove embodiments. Accordingly, this markedly improves utilizationefficiency of silicon fine particles for hydrogen generation as well assignificantly contributes to reduction in hydrogen production cost.

According to a different adoptable aspect, unlike the hydrogenproduction apparatus 200, there can be provided a means for supplyingsilicon fine particles into the surface oxide film removal tank 50 via aflow path connecting the reaction tank 72 and the surface oxide filmremoval tank 50 after the silicon fine particles in the reaction tank 72are separated from the water or the aqueous solution 75 by a filter. Thesilicon fine particles introduced into the surface oxide film removaltank 50 in such an aspect are also included in “silicon fine particlesextracted from the hydrogen generator” in the present application.According to a different adoptable aspect, the hydrophilizationtreatment step (the additional hydrophilization treatment step) isexecuted after the additional surface oxide film removing step, as inthe fourth embodiment.

In this aspect, the surface oxide film removing step and the additionalsurface oxide film removing step are executed using the same surfaceoxide film removal tank, and the hydrogen generating step and theadditional hydrogen generating step are executed using the same reactiontank 72. However, this aspect is not limited to this case. The surfaceoxide film removing step and the additional surface oxide film removingstep may be executed in different tanks, and the hydrogen generatingstep and the additional hydrogen generating step may be executed indifferent tanks.

Example 6

In the hydrogen generating step according to Example 6, immersed in theaqueous solution (0.1 mol/L of an aqueous potassium hydroxide solution)75 was 0.86 g of silicon fine particles, which were formed by grindingp-type silicon chips using a bead mill including beads made of ZiO₂ inthe same manner as in Example 5. Prepared in Example 6 were four typesof aqueous solutions 75 having pH values of 12.1, 12.9, 13.4, and 13.9with different addition amounts of potassium hydroxide (KOH).

The constant amount (0.86 g) of silicon fine particles were immersed ineach of the aqueous solutions at normal temperature to obtain the graphof hydrogen generation amounts with respect to a reaction period as inFIG. 11. In the case where the pH value is 13.9, it was found that thehydrogen generation amount per gram (g) of the silicon fine particlesreached about 1100 mL or more (i.e., about 1100 mL/g or more) within anextremely short period of time (within about 15 minutes from the startof reaction). It is noted that the hydrogen generation amount at the pHvalue of 13.9 exceeded 1000 mL per g of the silicon fine particles inthe period as short as about ten minutes. Neither the additional surfaceoxide film removing step nor the additional hydrogen generating step isexecuted at this stage.

FIG. 12 is a graph of a difference in maximum hydrogen generation speeddue to a difference in pH value in Example 6. The numerical values inFIG. 12 indicate maximum hydrogen generation speed per g in one minutein the four aqueous solutions having the different pH values indicatedin FIG. 11. It was found from the result indicated in FIG. 12 that themaximum hydrogen generation speed per g in one minute is clearlydependent on the pH value and increases as the pH value is larger. Thehydrogen generation speed can be controlled in accordance with thefeature that hydrogen generation speed is dependent on the pH value of asolution. Again, neither the additional surface oxide film removing stepnor the additional hydrogen generating step is executed at this stage.

The silicon fine particles, which have a saturated hydrogen generationamount or saturated hydrogen generation speed because reaction comesinto an equilibrium state in the case where the pH value is 13.9, weremeasured and analyzed using an XPS (X-ray photoelectron spectroscopy)analyzer. FIG. 13 is an XPS spectrography of the silicon fine particlesafter the hydrogen generation amount or the hydrogen generation speed issaturated in Example 6.

As indicated in FIG. 14, there was observed a plurality of Si_(2p) peaksbelonging to silicon (Si) and silicon dioxide (SiO₂). It was thus foundthat the silicon fine particles already or almost having reacted into anequilibrium state are formed with silicon dioxide (SiO₂) films on thesurfaces of the particles. According to the peak intensity ratio between(Si) and (SiO₂) indicated in FIG. 14, it was concluded that the siliconfine particles are formed with SiO₂ films of about 5 nm thick on thesurfaces of the particles.

Example 6 includes the step of removing the SiO₂ films by causing thesilicon fine particles already or almost having reacted into anequilibrium state to contact with a 5% aqueous HF solution (theadditional surface oxide film removing step). Subsequently, the siliconfine particles were immersed again in the aqueous solution 75 having apH value of 13.9. The silicon fine particles then generated further 470ml/g of hydrogen (per g of the initial silicon fine particles) (theadditional hydrogen generating step).

In Example 6, the sum of the initial hydrogen gas generation amount(until the saturated state) and the hydrogen gas generation amount afterthe additional surface oxide film removing step and the additionalhydrogen generating step was about 1570 mL per g of the silicon fineparticles. This is approximate to 1600 mL (theoretical value) as themaximum generation amount of hydrogen that can be generated in reactionwith 1 g of silicon in the aqueous solution 75. It was thus found thatthe additional surface oxide film removing step and the additionalhydrogen generating step were quite useful measures for generation of anextremely large amount of hydrogen.

Example 7

Described next is a different result of a hydrogen production test byusing the hydrogen production apparatus 100. In the hydrogen generatingstep according to Example 7, the aqueous solution 75 includes sodiumhydroxide or ammonia. At normal temperature, 0.86 g of silicon fineparticles was caused to contact with and/or disperse in the aqueoussolution 75 so as to be caused to react.

FIG. 14 is a graph of the hydrogen generation amount per g with respectto a reaction period in Example 7. An experiment value (a) is obtainedin a case of using 20 mL of an aqueous solution having a pH value of13.4 to which sodium hydroxide (NaOH, also referred to as caustic soda)is added. An experiment value (b) is obtained in a case of using 20 mLof an aqueous solution having a pH value of 11.9 to which ammonia (NH₃)is added. The graph in FIG. 14 has the transverse axis indicating theimmersion period (minute). The graph in FIG. 14 has the ordinate axisindicating the hydrogen generation amount (mL/g) per g of silicon fineparticles for hydrogen production.

When the silicon fine particles are immersed in the aqueous solution 75to which ammonia is added, the silicon fine particles may float on thesurface of the solution if the silicon fine particles are notparticularly treated preliminarily. For this reason, in Example 7,ethanol was added dropwise into the aqueous solution 75 to precipitatethe silicon fine particles to the bottom of the reaction tank 72. Thiscauses the silicon fine particles to contact with the aqueous solution75 to which ammonia is added. On the other hand, in the case of usingthe aqueous solution 75 to which sodium hydroxide is added, theexperiment was executed with the silicon fine particles caused tocontact with and/or disperse in the aqueous solution 75, similarly tothe case of using the solution to which potassium hydroxide is added.

As indicated in FIG. 14, it was found that the hydrogen generationamount or the hydrogen generation speed can be controlled by changingthe type or the pH value of the aqueous solution. According to anadoptable and very preferred aspect, the hydrogen generation speedand/or the hydrogen generation amount is adjusted by changing the pHvalue of the water or the aqueous solution 75 in the hydrogen generatingstep in each of the above embodiments. Similarly, according to anadoptable and very preferred aspect, the hydrogen generator 70 in thehydrogen production apparatus 100 or the additional hydrogen generator270 in the hydrogen production apparatus 200 further includes anadjuster configured to adjust the hydrogen generation speed and/or thehydrogen generation amount by changing the pH value of the water or theaqueous solution 75.

For example, the adjuster can be configured by a device provided with ameans for dropping a desired amount of the water or each of the aqueoussolutions (the aqueous solution to which NaOH is added, the aqueoussolution to which KOH is added, the aqueous solution to which NH₃ isadded, and the like) having a variable pH value for a desired period oftime, and a control means for controlling the pH value. Morespecifically, the dropping means can be configured to drop a desiredamount of a chemical substance for adjusting the pH value, such as NaOH,KOH, or NH₃, for a desired period of time so as to achieve a desired pHvalue, upon receipt of a feedback measurement result from a measurementunit configured to measure the pH value of the water or each of theaqueous solutions 75.

On the other hand, in consideration of the results of the examplesdescribed above, the pH value is preferably set to 10 or more and morepreferably to 11.9 or more in terms of obtaining a larger amount ofhydrogen in a shorter period of time.

The silicon fine particles are treated using the aqueous hydrofluoricacid solution in the surface oxide film removing step according to eachof the above examples. A preferred result similar to that of each of theexamples can be achieved also in a case where the silicon fine particlesare treated using an aqueous ammonium fluoride solution in place of oralong with the aqueous hydrofluoric acid solution.

The silicon fine particles are treated using the surfactant in thehydrophilization treatment step according to the above example. Apreferred result quite similar to that of the example can be achievedalso in a case where the silicon fine particles are treated using nitricacid in place of or along with the surfactant.

In each of the above embodiments, the treatment using the surfactant ornitric acid may not be performed in the independent hydrophilizationtreatment step but can be performed during the hydrogen generating stepby adding the surfactant or nitric acid to the water or the aqueoussolution used in the hydrogen generating step.

As described in Example 6, when silicon fine particles are added intothe water or the aqueous solution to be dispersed in the hydrogengenerating step, the silicon fine particles dissolve in the water or theaqueous solution and are formed with silicic acid on the surfaces of theparticles. The silicic acid is subsequently oxidized into silicondioxide (SiO₂), so that hydrogen generation reaction is inactivated orterminated as time elapses. In order to suppress formation of silicondioxide (SiO₂) on the surfaces of the silicon fine particles to continuehydrogen generation reaction, according to a different adoptablepreferred aspect, a small amount of hydrofluoric acid is added into thewater or the aqueous solution used in the hydrogen generating step tocause the silicon fine particles to contact with the water or theaqueous solution for continuous hydrogen generation reaction.

Each of the above embodiments adopts the hydrogen generator 70 or theadditional hydrogen generator 270 configured to generate hydrogen fromthe formed silicon fine particles (or aggregate thereof) which are notpositionally fixed but are caused to contact with and/or disperse in thewater or the aqueous solution 75. However, the method of causing siliconfine particles to contact with the water or the aqueous solution 75 isnot limited to the method described above. According to a differentadoptable aspect, the formed silicon fine particles firmly fixed onto asurface of a solid object (e.g. a sponge body) are caused to contactwith the water or the aqueous solution 75 so as to generate hydrogen. Ina case where the solid object is made of a material that can absorb andhold a certain amount of liquid like the sponge body, generation ofsilicon dioxide (SiO₂) on the silicon fine particles can be suppressedmore possibly by an aqueous hydrofluoric acid solution or an aqueousammonium fluoride solution impregnated into the solid object.

The above embodiments are disclosed for description of theseembodiments, not for limitation to the present invention. Furthermore,modification examples within the scope of the present invention,inclusive of other combinations of the embodiments, are also included inthe claims.

1. A hydrogen production apparatus comprising: a grinding unitconfigured to grind a silicon chip or a silicon grinding scrap to formsilicon fine particles; and a hydrogen generator configured to generatehydrogen by causing the silicon fine particles to contact with as wellas disperse in, or to contact with or dispersed in water or an aqueoussolution.
 2. The hydrogen production apparatus according to claim 1,further comprising: a surface oxide film remover configured to cause thesilicon fine particles formed by the grinding unit to contact with anaqueous hydrofluoric acid solution or an aqueous ammonium fluoridesolution; wherein the hydrogen generator generates hydrogen by causingthe silicon fine particles, which have been caused to contact with theaqueous hydrofluoric acid solution or the aqueous ammonium fluoridesolution, to contact with as well as disperse in, or to contact with ordispersed in water or an aqueous solution.
 3. The hydrogen productionapparatus according to claim 2, further comprising: a hydrophilizationtreatment unit configured to hydrophilize surfaces of the silicon fineparticles having been caused to contact with the aqueous hydrofluoricacid solution or the aqueous ammonium fluoride solution; wherein thehydrophilization treatment unit causes the surfaces of the silicon fineparticles to contact with a surfactant or nitric acid.
 4. The hydrogenproduction apparatus according to claim 1, further comprising: anadditional surface oxide film remover configured to cause the siliconfine particles extracted from the hydrogen generator to contact againwith an aqueous hydrofluoric acid solution or an aqueous ammoniumfluoride solution; and an additional hydrogen generator configured togenerate hydrogen by causing the silicon fine particles, which have beencaused to contact again with the aqueous hydrofluoric acid solution orthe aqueous ammonium fluoride solution by the additional surface oxidefilm remover, to contact with as well as disperse in, or to contact withor dispersed in water or an aqueous solution.
 5. The hydrogen productionapparatus according to claim 1, further comprising: an adjusterconfigured to adjust at least one of hydrogen generation speed and ahydrogen generation amount by changing a hydrogen ion concentrationindex (pH) of the water or the aqueous solution in the hydrogengenerator.
 6. A hydrogen production method comprising: a grinding stepof grinding a silicon chip or a silicon grinding scrap to form siliconfine particles; and a hydrogen generating step of generating hydrogen bycausing the silicon fine particles to contact with as well as dispersein, or to contact with or dispersed in water or an aqueous solution. 7.The hydrogen production method according to claim 6, further comprising:a surface oxide film removing step to be executed before the hydrogengenerating step, of causing the silicon fine particles formed in thegrinding step to contact with an aqueous hydrofluoric acid solution oran aqueous ammonium fluoride solution; wherein in the hydrogengenerating step, hydrogen is generated by causing the silicon fineparticles, which have been caused to contact with the aqueoushydrofluoric acid solution or the aqueous ammonium fluoride solution, tocontact with as well as disperse in, or to contact with or dispersed inwater or an aqueous solution.
 8. The hydrogen production methodaccording to claim 7, further comprising: a hydrophilization treatmentstep to be executed before the hydrogen generating step, ofhydrophilizing surfaces of the silicon fine particles having been causedto contact with the aqueous hydrofluoric acid solution or the aqueousammonium fluoride solution.
 9. The hydrogen production method accordingto claim 6, further comprising: an additional surface oxide filmremoving step to be executed during or after the hydrogen generatingstep, of causing the silicon fine particles to contact again with anaqueous hydrofluoric acid solution or an aqueous ammonium fluoridesolution; and an additional hydrogen generating step to be executedafter the additional surface oxide film removing step, of generatinghydrogen by causing the silicon fine particles to contact with as wellas disperse in, or to contact with or dispersed in the water or theaqueous solution again.
 10. The hydrogen production method according toclaim 6, wherein in the hydrogen generating step, at least one ofhydrogen generation speed and a hydrogen generation amount is adjustedby changing a hydrogen ion concentration index (pH) of the water or theaqueous solution.
 11. The hydrogen production method according to claim8, wherein in the hydrophilization treatment step, the surfaces of thesilicon fine particles are caused to contact with a surfactant or nitricacid.
 12. The hydrogen production method according to claim 6, whereinthe silicon fine particles have a crystallite diameter of 100 nm orless.
 13. The hydrogen production method according to claim 6, whereinthe aqueous solution used in the hydrogen generating step has a pH valueof 10 or more.
 14. A silicon fine particle for hydrogen production,having: an amorphous shape, a crystallite diameter of 100 nm or less,and a hydrophilic surface.
 15. The silicon fine particle for hydrogenproduction according to claim 14, having: a hydrophilic surface.
 16. Thesilicon fine particle for hydrogen production according to claim 14,including a silicon fine particle obtained by chemically treating asilicon fine particle that is formed by grinding a silicon chip or asilicon grinding scrap.
 17. A production method for silicon fineparticles for hydrogen production, the method comprising: a grindingstep of grinding a silicon chip or a silicon grinding scrap to formsilicon fine particles.
 18. The production method for silicon fineparticles for hydrogen production according to claim 17, the methodfurther comprising: a surface oxide film removing step of causing thesilicon fine particles formed in the grinding step to contact with anaqueous hydrofluoric acid solution or an aqueous ammonium fluoridesolution.
 19. The production method for silicon fine particles forhydrogen production according to claim 18, the method furthercomprising: a hydrophilization treatment step of hydrophilizing surfacesof the silicon fine particles having been caused to contact with theaqueous hydrofluoric acid solution or the aqueous ammonium fluoridesolution.
 20. The production method for silicon fine particles forhydrogen production according to claim 19, wherein in thehydrophilization treatment step, the surfaces of the silicon fineparticles are caused to contact with a surfactant or nitric acid. 21.The production method for silicon fine particles for hydrogen productionaccording to claim 17, the method further comprising: a chemicaltreatment step of chemically treating the silicon fine particles thatare formed by grinding the silicon chip or the silicon grinding scrap.22. A silicon fine particle for hydrogen production, the silicon fineparticle being produced in accordance with the production method forsilicon fine particles for hydrogen production according to claim 17.